1. Field of the Invention
The present invention relates to a control device for hybrid vehicles. More specifically, the present invention relates to a control device for a hybrid vehicle which enables improvement in salability at low vehicle speed and low revolution range of the engine.
2. Description of Related Art
Hybrid vehicles provided with a motor as an auxiliary driving source for running the vehicle in addition to an engine have been conventionally known.
A parallel hybrid vehicle in which output from an engine is auxiliary assisted by a motor is a variation of the hybrid vehicle. In the parallel hybrid vehicle, output from the engine is auxiliary assisted by the motor when the vehicle is accelerated, and various controls, such as stop of fuel supply and charging of batteries using deceleration regenerative braking, are performed when the vehicle is decelerated so that the needs of the driver can be satisfied while maintaining remaining charge of the batteries (as disclosed in, for instance, Japanese Unexamined Patent Application, First Publication No. 7-123509).
In some of the above-mentioned hybrid vehicles, especially in vehicles provided with manual transmission (so called MT vehicles), regenerative braking is performed in accordance with the revolution number of the engine in a deceleration mode when deceleration fuel cut is not carried out at low vehicle speed and the accelerator is not pressed as in the case of, for instance, traveling on a curve at low speed.
However, when the vehicle enters a deceleration mode and the revolution number of the engine further decreases, and regenerative braking is stopped in order to prevent engine stall, the regenerative braking is carried out again since the load on the engine decreases by the amount corresponding to the stop of the regenerative braking and the revolution number of the engine increases.
Accordingly, hunting of the revolution number of the engine is caused by repeating stop and restart of the regenerative braking. In particular, when a large braking force is applied to the engine by means of a brake control and regenerative braking, such as for the case where the brake pedal is pressed, shock generated by stopping and restarting the regenerative braking increases, and this is not preferable in terms of salability.
Accordingly, an object of the present invention is to provide a control device for a hybrid vehicle which enables improvement in salability by stopping unnecessary regenerative braking by taking into account the driver""s intention to stop the vehicle and by eliminating hunting of the revolution number of the engine within a low speed range.
In order to achieve the above object, the present invention provides a control device for a hybrid vehicle provided with an engine (for instance, an engine E in an embodiment described later) and a motor (for instance, a motor M in the embodiment described later) as driving sources, and a storage battery device (for instance, a battery 3 in the embodiment described later) which stores regenerative energy obtained by output from the engine or by regenerative operation of the motor during deceleration of the vehicle, the control device including: a vehicle speed detection unit (for instance, a vehicle speed sensor S1 in the embodiment described later) which detects speed of the vehicle; a deceleration fuel cut determination unit (for instance, a step S074 shown in FIG. 3 in the embodiment described later) which determines whether supply of fuel to the engine is stopped during deceleration of the vehicle; and a brake detection unit (for instance, a brake switch S4 in the embodiment described later) which detects operation of a brake, wherein regenerative braking is stopped (for instance, a cruise mode shown in step S077 in the embodiment described later) when operation of the brake is detected by the brake detection unit (for instance, xe2x80x9cYESxe2x80x9d in step S074C in the embodiment described later) if the vehicle speed detected by the vehicle speed detection unit is lower than a predetermined speed and if it is determined by the deceleration fuel cut determination unit that the supply of fuel to the engine is not stopped (for instance, xe2x80x9cNOxe2x80x9d in step S074 in the embodiment described later).
In accordance with another aspect of the invention, in the control device for a hybrid vehicle, the vehicle is further provided with a manual transmission (for instance, a manual transmission (MT) T in the embodiment described later).
According to the above control device for a hybrid vehicle, since the regenerative braking can be stopped by taking into account the driver""s intention to stop when the brake pedal is applied if the vehicle speed is lower than a predetermined speed and it is not during a deceleration fuel cut state, it becomes possible to prevent hunting, in which increase and decrease of the engine revolution number is repeated as in the case where regenerative operation is continued, and hence the salability can be improved. Also, since the vehicle speed is low and the brake is applied, the degree of regenerative amount that can be obtained is small and no adverse effect is imparted on energy management.
The present invention also provides a control device for a hybrid vehicle provided with an engine (for instance, an engine E in an embodiment described later) and a motor (for instance, a motor M in the embodiment described later) as driving sources, and a storage battery device (for instance, a battery 3 in the embodiment described later) which stores regenerative energy obtained by output from the engine or by regenerative operation of the motor during deceleration of the vehicle, the control device including: a vehicle speed detection unit (for instance, a vehicle speed sensor S1 in the embodiment described later) which detects speed of the vehicle; a deceleration fuel cut determination unit (for instance, a step S074 shown in FIG. 3 in the embodiment described later) which determines whether supply of fuel to the engine is stopped during deceleration of the vehicle; a brake detection unit (for instance, a brake switch S4 in the embodiment described later) which detects operation of a brake, and a throttle opening degree detection unit (for instance, a throttle opening degree sensor S6 in the embodiment described later) which detects an opening degree of a throttle, wherein regenerative braking is carried out with a degree corresponding to a revolution number of the engine (as shown in, for instance, FIG. 5 which indicates setting of the regenerative amount in the deceleration mode in step S078, and step S104), if the opening degree of throttle detected by the throttle opening degree detection unit is smaller than a predetermined value (for instance, xe2x80x9cNOxe2x80x9d in step S074D in the embodiment described later), when the vehicle speed detected by the vehicle speed detection unit is lower than a predetermined speed, it is determined by the deceleration fuel cut determination unit that the supply of fuel to the engine is not stopped (for instance, xe2x80x9cNOxe2x80x9d in step S074 in the embodiment described later), and the operation of brake is not detected by the brake detection unit (for instance, xe2x80x9cNOxe2x80x9d in step S074C in the embodiment described later).
According to the above control device for a hybrid vehicle, it becomes possible to set an appropriate regenerative amount in accordance with the engine revolution number when a proper deceleration state is determined based on the throttle opening degree. Accordingly, regenerative operation can be smoothly performed.